A number of processes have been reported for the preparation of mono- and disubstituted ureas and amines as in the preparation of, for example, the bis (diethylurea) of toluenediamine by reacting toluene-2,4-diisocyanate with diethylamine described in French Pat. No. 1,570,670.
An article by N.A. Ivanov entitled "Synthesis of Substituted Ureas and Thioureas and Their Thermal Stability", Chemistry Department of the Kalinin Agricultural Institute, describes the synthesis of thioureas, monosubstituted ureas and disubstituted ureas of toluene-2,4-diamine.
German Democratic Republic Industrial Patent No. 228,544 related to the production of acyl isocyanates describes the synthesis of 1, 1'-diacyl-3, 3-dialkylureas from, for example 1, 1-dimethylurea.
Czechoslovakian Patent No. 200,441 discloses a method for the preparation of aminophenylurea by reacting phenylenediamine with one mole of cyanic acid in the presence of sodium or potassium cyanate.
An article of Y. Shimonura et al entitled "Reactions of Isocyanic Acid with Various Reagents", Fukui Daigaku Kogakuba Kenkyu Hokoku, Vol. 31, No. 2, pp 115, 1983 describes the reaction of 2-cyanoethylamine with isocyanic acid to give 2-cyanoethylurea. The synthesis of isocyanic acid from cyanuric acid by thermal decomposition is also set forth.
Applicants are not aware of any truly pertinent prior art that is deemed to be anticipatory or suggestive of the concept of the present invention. cl SUMMARY OF THE INVENTION
This invention relates to a novel method for the preparation of aromatic bis dialkyl ureas which may be used in agricultural applications as insecticides and herbicides or further processed to useful isocyanate products. Aromatic diamines are reacted with isocyanic acid (HNCO) to convert the amino groups to urea groups (--NHCONH.sub.2) which urea compounds are then reacted with a dialkyl amine to produce the desired aromatic bis dialkyl ureas.
The primary object of the present invention is to provide an improved process for the preparation of aromatic bis dialkyl ureas in high yield and high conversion of reactants
It is another object of this invention to provide an improved reaction system for the conversion of aromatic diamines such as toluene-2,4- and 2,6-toluenediamine to aromatic bis (dialkyl) ureas.
These and other objects and advantages of this invention will become apparent from the description of the invention which follows, and from the claims.